Bone marrow examinations have been conducted either by blood clotting or filtration of the blood to recover the cells or specimens. In the former, the aspirated marrow particles which are removed with the blood are separated by clotted blood. In the filtration technique, the particles are recovered with the sinusoidal blood that are filtered from the blood for analysis. A number of publications discuss these procedures and their relative merits. For instance, "Bone Marrow Histology, Aspiration versus Biopsy", by Drs. A. M. Rywlin and B. Drewinko, A.J.C.P., pp. 617-618, Vol. 66, September, 1976; Letters to the Editor, "The Relative Merits of Bone Marrow Biopsy and Particle Section Technics", by Drs. R. S. Neiman, A. Coppola and T. Athanassiades, A.J.C.P., pp. 308-309, Vol. 67, No. 3; and "Bone Marrow Examinations", by Dr. B. O'Neill, pp. 21-22, The Medical Journal of Australia, Jan. 13, 1979.
In the conventional procedure, a bone marrow needle is inserted with a trocar into a bone marrow cavity at the intended site. An aspirator is then attached to the exposed end of the needle whereby application of a vacuum will induce the removal of sinusoidal blood along with any dislodged particles of the bone marrow through the needle into the aspirator. The aspirator is then removed and the blood passed through a suitable filtering device or onto a glass plate to aid in removal of any of the bone marrow particles from the blood. These particles are then placed or smeared on a slide for analysis.
In filtering the bone marrow particles from a quantity of blood recovered from the bone marrow, it may be difficult to obtain an adequate specimen for analysis. Also it requires the collection of the blood in a container such as a syringe followed by removal and separate filtration and is therefore time-consuming. Thus, if the specimen is inadequate, the entire procedure must be repeated and can cause a great deal of unnecessary discomfort to the patient as well as increased expense.
Various devices have been utilized in other medical or surgical procedures in which cells or tissue are withdrawn by vacuum onto a filter, then the filter removed and the sample scraped onto a slide for analysis. For example, representative U.S. patents are those to Molomut et al U.S. Pat. No. 3,224,434; Denis U.S. Pat. No. 3,889,682; and Baumgarten, U.S. Pat. No. 3,889,657.
Other devices employ a vacuum for removal of a liquid such as saliva in dental surgery and employ a filter or trap to separately collect the foreign particles. See, for example, U.S. patent to Berger, U.S. Pat. No. 3,706,305; Carritt et al U.S. Pat. No. 3,000,805; and Wiley U.S. Pat. No. 4,083,706. However, in these cases the filter or trap is employed more for the purpose of collecting foreign matter on a filter, but are not concerned with removal of the foreign matter from the filter or analysis of the foreign matter.
Other instruments have been devised for removal of the blood from a vein by injecting a needle into the vein and applying a vacuum to draw the blood into a syringe or container. For example, see U.S. patent to Worrall, Jr., U.S. Pat. No. 3,382,865; Sachs U.S. Pat. No. 3,965,889; and Bridgman U.S. Pat. No. 3,833,000. However in the past the vacuum or aspiration devices which include a trap for recovery of foreign matter are not so devised that fine particles can be selectively collected on the surface of a filter within a vacuum chamber in the path of the flow of blood from the bone marrow site, following which the chamber can be opened to immediately expose the filter and particles collected on the filter for removal.